IPSEC connection problems

[cube]

Hi Guys, I'm having a nightmare time getting a site to site VPN system setup and was really hoping you can point me in the right direction.

The setup:

We have a head office (site A)  running a leased line 100/100 and a branch office (Site B) with BT infinity 80/20

Both have pfsense firewalls on version 2.2.4

Site B has a BT Business hub which I've put in bridging mode to give the public IP to the WAN interface.  Site B's WAN interface is PPPoE and is picking up the details.

Site A can connect to internet, everything perfect.

From Site B when I connect the tunnel - using a computer attached to the LAN I can ping all the devices on the remote network, can use remote desktop to connect to them, access the exchange server basically everything seems to work well.

I can also access computers using team viewer, so I know they are connected to the internet.

The odd behavior is on websites. Some work fine and fast.  Google sites (news, maps etc, youtube) all load fine, as does www.theguardian.com/uk.

Most other sites dont load though.  They begin to load, I often get background images etc, but they stop (maybe when trying to load adverts?).

I'm really confused why it is happening on some sites but not others.

My first question is, could the hardware at Site A be causing problems?  It was built with a fairly old Dell desktop (it was only meant to be a proof of concept before investing in some more expensive hardware).  If a lack of hardware is known to cause behavior like this I'll stop tearing my hair out and invest some cash.

I've searched around but cant find anyone who seems to be having the same kind of problems I'm having, so if anyone recognizes these symptoms I would be eternally grateful!

I can provide any more info if its needed needed to help.

Thanks in Advance

Cube

Rapidly Balding IT Guy

[cmb]

Likely just need to enable MSS clamping on the advanced tab.